Tracing legacy and emerging PFAS contamination in mangrove ecosystems across South China: Insights into partitioning and socioeconomic influences

Mangrove ecosystems, located at the land-sea interface, are especially susceptible to land-based runoff carrying persistent environmental pollutants such as per - and polyfluoroalkyl substances (PFAS). Despite their ecological importance, the dynamics of PFAS contamination in China's mangroves remain poorly understood. We systematically assessed 15 mangrove wetlands across four southern provinces, revealing significant spatial variation in PFAS contamination. Mangrove sediments from Fujian exhibited significantly higher levels of PFOA and ΣPFAS compared to the other three provinces, while Guangdong showed notably higher concentrations of FOSA and N-EtFOSAA. PFOS and FOUEA levels were also significantly higher in Fujian and Guangdong than in Guangxi and Hainan, whereas PFPeA, PFTeDA, PFHxS or 6:2 FTS showed no significant differences. Sediment PFAS profiles across the four provinces showed some overlap, particularly for C 5 − C 7 PFCAs, C 4 and C 6 PFSAs, N-EtFOSAA and NaDONA. In contrast, surface seawater from Beihai and Guangzhou displayed distinct PFAS compositions: Beihai was dominated by PFBA, while Guangzhou had higher ratios of PFBS, C 6 − C 8 PFCAs, and 6:2 FTS. Both log K D and log K OC values exhibited significant positive correlations with carbon-chain length, with emerging PFAS (except 6:2 FTS) exhibiting comparable or higher log K OC values than long-chain PFAAs. Socioeconomic indicators, including population size, GDP, and urbanization rate, were positively correlated with long-chain PFAAs, and negative correlations with short-chain PFAAs, suggesting that urbanization and industrialization are potential factors associated with PFAS contamination patterns in mangrove sediments, and contributed to elevated PFOS risk in parts of Fujian and Guangdong.